The importance of the age factor in cancer vaccination at older age

Reverse geroscience: how does exposure to early diseases accelerate the age-related decline in health?

Aging is the major risk factor for both the development of chronic diseases and loss of functional capacity. Geroscience provides links among the biology of aging, the biology of disease, and the physiology of frailty, three fields where enormous progress has been made in the last few decades. While, previously, the focus was on the role of aging in susceptibility to disease and disability, the other side of this relationship, which is the contribution of disease to aging, has been less explored at the molecular/cellular level. Indeed, the role of childhood or early adulthood exposure to chronic disease and/or treatment on accelerating aging phenotypes is well known in epidemiology, but the biological basis is poorly understood. A recent summit co-organized by the National Institutes of Health GeroScience Interest Group and the New York Academy of Sciences explored these relationships, using three chronic diseases as examples: cancer, HIV/AIDS, and diabetes. The epidemiological literature clearly indicates that early exposure to any of these diseases and/or their treatments results in an acceleration of the appearance of aging phenotypes, including loss of functional capacity and accelerated appearance of clinical symptoms of aging-related diseases not obviously related to the earlier event. The discussions at the summit focused on the molecular and cellular relationships between each of these diseases and the recently defined molecular and cellular pillars of aging. Two major conclusions from the meeting include the desire to refine an operational definition of aging and to concomitantly develop biomarkers of aging, in order to move from chronological to physiological age. The discussion also opened a dialogue on the possibility of improving late-life outcomes in patients affected by chronic disease by including age-delaying modalities along with the standard care for the disease in question.

Immunotherapy for canine cancer--is it time to go back to the future?

Over the last 50 years, the significance of the immune system in the development and control of cancer has been much debated. However, recent discoveries provide evidence for a role of immunological mechanisms in the detection and destruction of cancer cells. Forty years ago veterinary oncologists were already investigating the feasibility of treating neoplasia by enhancing anticancer immunity. Unfortunately, this research was hindered by lack of a detailed understanding of cancer immunology, this limited the specificity and success of these early approaches. The great forward strides made in our understanding of onco-immunology in recent years have provided the impetus for a resurgence of interest in anticancer immunotherapy for canine patients. In this article both these initial trials and the exciting novel immunotherapeutics currently in development are reviewed.

Aging and cancer vaccines

Cancer vaccination is less effective at old than at young age, due to T cell unresponsiveness. This is caused by age-related changes of the immune system. Major immune defects at older age are lack of naive T cells, impaired activation pathways of T cells and antigen-presenting cells (APC), and age-related changes in the tumor microenvironment (TME). Also innate immune responses are affected by aging, but this seems less abundant than adaptive immune responses. In this review we compared various cancer vaccine studies at young and old age, demonstrating the importance of both innate and adaptive immune responses for cancer immunotherapy. Moreover, we found suggestive evidence that innate immune responses could help improve adaptive immune responses through cancer vaccination in old age.

Is cancer vaccination feasible at older age?

Age-related defects of the immune system are responsible for T cell unresponsiveness to cancer vaccination at older age. Major immune defects at older age are lack of naive T cells, impaired activation pathways of T cells and antigen-presenting cells (APCs), and age-related changes in the tumor microenvironment (TME). This raises the question whether cancer vaccination is feasible at older age. We compared various cancer vaccine studies at young and old age, thereby focusing on the importance of both innate and adaptive immune responses for cancer immunotherapy. These analyses suggest that creating an immune-stimulating environment with help of the innate immune system may improve T cell responses in cancer vaccination at older age.

T cell replicative senescence in human aging

The decline of the immune system appears to be an intractable consequence of aging, leading to increased susceptibility to infections, reduced effectiveness of vaccination and higher incidences of many diseases including osteoporosis and cancer in the elderly. These outcomes can be attributed, at least in part, to a phenomenon known as T cell replicative senescence, a terminal state characterized by dysregulated immune function, loss of the CD28 costimulatory molecule, shortened telomeres and elevated production of proinflammatory cytokines. Senescent CD8 T cells, which accumulate in the elderly, have been shown to frequently bear antigen specificity against cytomegalovirus (CMV), suggesting that this common and persistent infection may drive immune senescence and result in functional and phenotypic changes to the T cell repertoire. Senescent T cells have also been identified in patients with certain cancers, autoimmune diseases and chronic infections, such as HIV. This review discusses the in vivo and in vitro evidence for the contribution of CD8 T cell replicative senescence to a plethora of age-related pathologies and a few possible therapeutic avenues to delay or prevent this differentiative end-state in T cells. The age-associated remodeling of the immune system, through accumulation of senescent T cells has farreaching consequences on the individual and society alike, for the current healthcare system needs to meet the urgent demands of the increasing proportions of the elderly in the US and abroad.

Proposed mechanisms of action for prostate cancer vaccines

Prostate cancer is responsible for the deaths of more than 33,000 American men every year. Once this disease has become metastatic, there is no curative treatment. Alternative therapies to chemotherapy and radical prostatectomy are being increasingly explored. Prostate cancer vaccines--which trigger a tumour-specific cytotoxic-T-lymphocyte-mediated immune attack by the patient's immune system--have been investigated in clinical trials with modest, yet encouraging, results. When developing and administering prostate cancer vaccines, it is critical to consider how vital parameters, such as the stage of disease progression and the nature of adjuvant therapies, could influence treatment outcome. Of particular interest are current and future strategies for diminishing the activity of regulatory T lymphocytes.

T cell replicative senescence in human aging

The decline of the immune system appears to be an intractable consequence of aging, leading to increased susceptibility to infections, reduced effectiveness of vaccination and higher incidences of many diseases including osteoporosis and cancer in the elderly. These outcomes can be attributed, at least in part, to a phenomenon known as T cell replicative senescence, a terminal state characterized by dysregulated immune function, loss of the CD28 costimulatory molecule, shortened telomeres and elevated production of proinflammatory cytokines. Senescent CD8 T cells, which accumulate in the elderly, have been shown to frequently bear antigen specificity against cytomegalovirus (CMV), suggesting that this common and persistent infection may drive immune senescence and result in functional and phenotypic changes to the T cell repertoire. Senescent T cells have also been identified in patients with certain cancers, autoimmune diseases and chronic infections, such as HIV. This review discusses the in vivo and in vitro evidence for the contribution of CD8 T cell replicative senescence to a plethora of age-related pathologies and a few possible therapeutic avenues to delay or prevent this differentiative end-state in T cells. The age-associated remodeling of the immune system, through accumulation of senescent T cells has farreaching consequences on the individual and society alike, for the current healthcare system needs to meet the urgent demands of the increasing proportions of the elderly in the US and abroad.

Aging, cancer, and cancer vaccines

World population has experienced continuous growth since 1400 A.D. Current projections show a continued increase - but a steady decline in the population growth rate - with the number expected to reach between 8 and 10.5 billion people within 40 years. The elderly population is rapidly rising: in 1950 there were 205 million people aged 60 or older, while in 2000 there were 606 million. By 2050, the global population aged 60 or over is projected to expand by more than three times, reaching nearly 2 billion people [1]. Most cancers are age-related diseases: in the US, 50% of all malignancies occur in people aged 65-95. 60% of all cancers are expected to be diagnosed in elderly patients by 2020 [2]. Further, cancer-related mortality increases with age: 70% of all malignancy-related deaths are registered in people aged 65 years or older [3]. Here we introduce the microscopic aspects of aging, the pro-inflammatory phenotype of the elderly, and the changes related to immunosenescence. Then we deal with cancer disease and its development, the difficulty of treatment administration in the geriatric population, and the importance of a comprehensive geriatric assessment. Finally, we aim to analyze the complex interactions of aging with cancer and cancer vaccinology, and the importance of this last approach as a complementary therapy to different levels of prevention and treatment. Cancer vaccines, in fact, should at present be recommended in association to a stronger cancer prevention and conventional therapies (surgery, chemotherapy, radiation therapy), both for curative and palliative intent, in order to reduce morbidity and mortality associated to cancer progression.

Interdisciplinary critique of sipuleucel-T as immunotherapy in castration-resistant prostate cancer

Sipuleucel-T was approved by the US Food and Drug Administration on April 29, 2010, as an immunotherapy for late-stage prostate cancer. To manufacture sipuleucel-T, mononuclear cells harvested from the patient are incubated with a recombinant prostatic acid phosphatase (PAP) antigen and reinfused. The manufacturer proposes that antigen-presenting cells exogenously activated by PAP induce endogenous T-cells to attack PAP-bearing prostate cancer cells. However, the lack of demonstrable tumor responses has prompted calls for scrutiny of the design of the trials in which sipuleucel-T demonstrated a 4-month survival benefit. Previously unpublished data from the sipuleucel-T trials show worse overall survival in older vs younger patients in the placebo groups, which have not been shown previously to be prognostic for survival in castration-resistant prostate cancer patients receiving chemotherapy. Because two-thirds of the cells harvested from placebo patients, but not from the sipuleucel-T arm, were frozen and not reinfused, a detrimental effect of this large repeated cell loss provides a potential alternative explanation for the survival "benefit." Patient safety depends on adequately addressing this alternative explanation for the trial results.

The impact of aging on cancer vaccination

Cancer vaccination is less effective at old than at young age, due to T cell unresponsiveness, caused by various age-related changes of the immune system. This includes lack of naïve T cells, defects in activation pathways of T cells and antigen-presenting cells (APC), and age-related changes in the tumor microenvironment. Although evidence exists that also natural killer (NK) and natural killer T (NKT) cells of the innate immune system change with age, comparison of various studies involving adaptive and innate immune responses in elderly and cancer patients, as well as cancer vaccination at young and old age in this review, indicates that also innate immune responses should be tested as a potential candidate to improve immunotherapy against cancer at older age.

Potential role of immunosenescence in cancer development

The incidence and prevalence of most cancers increase with age. The reasons for this may include tumor escape mechanisms and decreased immunosurveillance, but most are caused by the time required for carcinogenesis, according to most scientists. The immune system is a unique mechanism of defense against pathogens and possibly cancers; however, there is a body of evidence that the immune system of the aged is eroded, a phenomenon termed immunosenescence. There is a growing interest in immunosenescence and how it may contribute to the increased number of cancers with aging. Each arm of the immune system, innate and adaptive, is altered with aging, contributing to increased tumorigenesis. Understanding the contribution of immunosenescence to cancer development and progression may lead to better interventions for the elderly.

Senescence of the human immune system

The umbrella term 'immunosenescence' is applied to describe age-associated failing systemic immunity and is believed to contribute to the increased incidence and severity of infectious disease in old animals and people. Very limited studies in man have begun to reveal biomarkers of immune ageing ('immune signatures') increasingly recognized as an 'immune risk profile' (IRP) predicting mortality in the elderly. Even more limited studies in companion animals seem consistent with the idea that most or all other mammals may also show an IRP. It is of practical and scientific interest to more accurately determine the IRP and to devise interventions to modulate immune ageing. In man, cytomegalovirus (CMV) infection has an enormous impact on biomarkers associated with immunosenescence; it is not clear whether the same is true for a persistent viral infection in other animals. A significant fraction of the human immune system is committed to controlling CMV; this commitment increases with age and may itself cause pathology as a result of maintaining higher systemic levels of inflammatory mediators. It will be interesting to test whether similar phenomena occur in relatively long-lived animals, often sharing a human environment, like cats and dogs, and whether interventions to restore appropriate immunity in companion animals might also be applicable to people.